Concrete Volume Calculator

Calculate how much concrete you need for your project. This calculator helps you determine cubic yards, cubic feet, and number of bags needed for slabs, footings, walls, and columns. Always order 5-10% extra to account for waste and variations.

How to Calculate Concrete Volume

Rectangular Slab/Patio

Volume = Length × Width × Thickness

Example: 10' × 10' × 4" = 10 × 10 × (4/12) = 33.33 cubic feet = 1.23 cubic yards

Circular Column

Volume = π × (Diameter/2)² × Height

Example: 12" diameter × 48" height = π × (0.5)² × 4 = 3.14 cubic feet = 0.12 cubic yards

Wall

Volume = Length × Width × Height

Example: 20' × 8" × 6' = 20 × (8/12) × 6 = 80 cubic feet = 2.96 cubic yards

Concrete Coverage

Bag Sizes

80lb bag: 0.6 cubic feet (most common)
60lb bag: 0.45 cubic feet
40lb bag: 0.3 cubic feet (small projects)

Ready-Mix Concrete

Ordered in cubic yards. Minimum orders typically 1-2 cubic yards. Most common for larger projects.

Common Project Thicknesses

Sidewalks: 4 inches
Driveways: 4-6 inches (residential), 6-8 inches (heavy vehicles)
Patios: 4 inches
Footings: 8-12 inches (varies by load and soil)
Foundation walls: 8-12 inches
Slabs on grade: 4-6 inches

Example Calculations

10' × 10' Patio, 4" thick

Volume: 10 × 10 × (4/12) = 33.33 cubic feet

Cubic yards: 33.33 / 27 = 1.23 cubic yards

Bags: 33.33 / 0.6 = 56 bags (80lb) - add 5-10% = 59-62 bags

Order: 1.5 cubic yards (with 10% extra)

20' × 12' Driveway, 6" thick

Volume: 20 × 12 × (6/12) = 120 cubic feet

Cubic yards: 120 / 27 = 4.44 cubic yards

Order: 5 cubic yards (with 10% extra)

Waste and Overage

Always add extra concrete for:

Waste: Spillage, over-pouring (5-10%)
Uneven ground: Variations in depth (5%)
Forms: Extra for form edges and corners
Safety margin: Better to have extra than run short

Rule of thumb: Add 10% to calculated volume, then round up.

Ordering Tips

Calculate accurately: Measure carefully, account for all areas
Add 10% extra: For waste and variations
Round up: Order full cubic yards (ready-mix) or extra bags
Consider delivery: Minimum orders may apply for ready-mix
Plan timing: Concrete sets quickly, have everything ready
Weather check: Don't pour in freezing temperatures

Cost Estimates

Bagged Concrete

80lb bag: $4-8 per bag
60lb bag: $3-6 per bag
More expensive but convenient for small projects

Ready-Mix Concrete

$100-150 per cubic yard (varies by region)
More economical for larger projects
Delivery fees may apply
Minimum order typically 1-2 cubic yards

Concrete Mix Types

Standard mix: General purpose (3000-4000 PSI)
High-strength: Driveways, heavy loads (4000+ PSI)
Fast-setting: Quick repairs, cold weather
Fiber-reinforced: Reduces cracking

Preparation Checklist

✓ Calculate volume accurately
✓ Add 10% for waste
✓ Order concrete (bags or ready-mix)
✓ Prepare forms and base
✓ Have tools ready (trowel, screed, float)
✓ Plan for weather
✓ Arrange help (concrete is heavy!)

Pro Tip: For ready-mix concrete, always order slightly more than calculated. It's much cheaper to order an extra 0.5 cubic yards than to have a second delivery. Most companies will take back unused concrete if you haven't mixed it, but check their policy. For bagged concrete, buy extra bags - you can return unopened bags!

Concrete Volume Calculator